One-Step Synthesis of the Nanostructured AgI/BiOI Composites with Highly Enhanced Visible-Light Photocatalytic Performances

Abstract

The nanostructured AgI/BiOI composites were prepared by a facile, one-step, and low temperature chemical bath method with Bi(NO₃)₃, AgNO₃, and KI. Several characterization tools, such as X-ray powder diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), the Brunauer−Emmett−Teller (BET) surface area, photoluminescence (PL) spectra, and UV−vis diffuse reflectance spectroscopy, were employed to study the phase structures, morphologies, and optical properties of the samples. The PL intensity of AgI was greatly decreased when combined with BiOI, indicating the corresponding decreased recombination of the carriers. The photocatalytic properties of the as-prepared products were measured with the degradation of methyl orange and phenol at room temperature under visible light irradiation. The AgI/BiOI composites showed much higher photocatalytic performances over BiOI as well as AgI. It was also found that the AgI amount in the AgI/BiOI composites played an important role in the corresponding photocatalytic properties and the optimized ratio was obtained at 20%. The dramatic enhancement in the visible light photocatalytic performance of the AgI/BiOI composites could be attributed to the effective electron−hole separations at the interfaces of the two semiconductors, which facilitate the transfer of the photoinduced carriers. By the detection of hydroxyl radicals through a fluorescence technique, the photoinduced holes (h_VB⁺) were considered to be the dominant active species in the photodegradation process, which was also deduced from the theoretical speculations. The photocatalytic performances of the AgI/BiOI composites were maintained for the cycling experiments. In addition, based on the XRD and XPS patterns of the AgI/BiOI composites before and after reaction, AgI was stable in the composites under visible irradiation, indicating that AgI/BiOI composites could be used as stable and efficient visible-light-induced photocatalysts.